This invention relates to a filtering system by which liquids may be clarified by separating constituents suspended in the liquids from a filtrate. More particularly, this invention relates to a dual manifold filtering system by which a liquid may be cleansed of suspended particles by passing the liquid, under a pressure differential, through a plurality of fabric covered filter elements, each of which is coated with a pulverulent, such as diatomaceous earth, which transmits the liquid and captures the particles. The two manifolds of the filtering systems, located at either end of the filter elements, allow the filter elements to be thoroughly cleansed of the captured particles, during backwashing operations, from both ends of the filter elements.
Filtering systems for filtering fluids, such as water for use in a swimming pool or the like, are well-known and include those types in which multiple filter elements that can be coated with a special pulverulent material, such as diatomaceous earth (DAE), are provided in a filter tank or other vessel. A pressure differential in the fluid being filtered is maintained at opposite sides of each filtering element. Valving means are also conventionally provided with such systems, which allow the fluid flow through the filters to be reversed.
The filter elements may take many forms. For example, they may be in the form of porous or finely perforated, vertically aligned, curved or flat rectangular plates or cylindrical tubes. The plates comprise one or more hollow, rectangular inner support elements, which are perforated in a grid-like pattern. The elements are radially equidistantly disposed about an axis parallel to the longitudinal axis of the filter tank, and have one or more support ribs. The inner support element is encased within an outer, fine mesh cloth (made of polyester or other material) which passes water but retains the DAE particles. Similarly, the tubes may comprise one or more layers of fine mesh wire screen mounted on rigid supports such as wire frames.
Existing DAE filtering systems are single manifold systems. Thus, in current practice the multiple filter elements are in an integral relationship with a single manifold structure, located at one end of the filter tank, that collects the filtered water for downstream delivery, for example, into a swimming pool. In the operation of such filter elements, fluid containing a fine powder in suspension, generally a DAE, is forced through the porous filter elements (plates or tubes) and the powder accumulates on the surface of the elements so as to reduce the size of the interstices or perforations on the element wall and thus enhance the filtering operation and ensure the removal from the fluid of particles suspended therein. In operation, when the filtering cycle is stopped, the accumulated DAE layer falls off the outer surface of the elements. However, it has been found that accumulated DAE particles tend not to fall off at the corners and sides of such outer surfaces. Thus, often the DAE powder or the like accumulates and builds up on and in the spaces between the filter elements. Therefore, it is necessary periodically to remove accumulated powders from the filter plates or tubes to prevent clogging thereof.
The removal of the accumulated layer of powder or xe2x80x9csludgexe2x80x9d, is usually effected by a so called backwash operation wherein liquid is forced from the manifold through the filter elements (plates or tubes) in a direction opposite to that in which the liquid flowed during the filtering operation. In the existing single manifold systems, it has been extremely difficult and sometimes impossible, to completely remove the accumulated layer of powder and sludge from the filter elements, and too often the sludge builds up or xe2x80x9cbridgesxe2x80x9d, in the spaces between the filter elements, which seriously interferes with the removal of sludge from the filter.
Once a filter system is installed it has been found that substantially one hundred percent of the maintenance is in the cleaning of the filter of the dirt and sludge that it collects. Therefore, efficient backwashing is the key to cost-effective operation and maintenance of filter systems. Because the backwashing operation in existing filter systems, which are single manifold systems, suffers from poor efficacy, there is a need for an improved filter system.
The present invention provides an ingenious solution to the problem of poor backwashing. It does so based on the recognition that the xe2x80x9cbridgingxe2x80x9d, normally takes place at that end of the filter elements that is opposite to the manifold. Therefore, the problem of poor backwashing lies in the fact that a single manifold design can only effectuate adequate backwashing in that half of the element that is closest to the manifold.
In accordance with the present invention, there is provided a dual manifold filter system comprising a plurality of filter elements, each of said filter elements having a first end and a second end, a first structure which includes a first manifold, said first manifold having a connecting end that allows liquid to flow in or out of the first manifold, and an element connecting end with means to couple the first end of each of the filter elements to the first manifold and a second structure which includes a second manifold, said second manifold also having a connecting end that allows liquid to flow in or out of the second manifold, and an element connecting end with means to couple the second end of each of said filter elements to said second manifold. Such a dual manifold system allows the liquid to flow into the filter elements from either end during the backwashing cycle.
In another embodiment of the present invention, the filter system is comprised of walls defining a closed chamber having a first end, a second end and sides, inlet hydraulic conduit means at the first end of said chamber for admitting liquid to be filtered, a plurality of filter elements within said chamber, each of said filter elements having a first rod-shaped end and a second rod-shaped end projecting from said filter element, a first structure which includes a first manifold near the first end of the chamber, said first manifold having a chamber connecting end that allows liquid to flow in or out of the first manifold, and an element connecting end with means to couple the first rod-shaped end of each of the filter elements to the first manifold, a second structure which includes a second manifold near the second end of said chamber, said second manifold having a chamber connecting end that allows liquid to flow in or out of the second manifold, and an element connecting end with means to couple the second rod-shaped end of each of said filter elements to said second manifold, a first hydraulic means having a first end coupled to the chamber connecting end of the first manifold for conducting liquid to and from the first manifold, and a second end connected to the chamber and extending externally therethrough, a second hydraulic means having a first end coupled to the chamber connecting end of the second manifold for conducting liquid to and from the second manifold, and a second end connected to the chamber and extending externally therethrough, and means carried by said chamber wall for supporting the unit of filter elements. The supporting means for supporting the unit of filter elements may be co-acting with the first and second hydraulic conduit means to maintain the filter elements in a fixed predetermined relation within the chamber and permit ready removal of the elements from the chamber as a unit. The supporting means may also be in the form of a throughbolt that goes from the top to the bottom of the chamber through the manifolds.
The filter elements of the filter system may be comprised of a support frame, and a flexible outer sleeve encasing the support frame, said outer sleeve formed of a material having a multiplicity of interstices therein which pass fluid therethrough but are small enough to prevent diatomaceous earth particles from passing through, said outer sleeve being tightly wrapped over, and scaled at both ends to said support frame providing a rigid unitary structure therewith, said outer sleeve being open at the first rod-shaped end and the second rod-shaped end and adapted at said first and second rodlike ends to couple to the channel connecting ends of the first and second manifolds, respectively.
The filter elements of the filter system may be such that the material that forms the outer sleeve of the filter elements is braided or woven synthetic plastic fiber. Similarly, the support frame of the filter elements may be comprised of a moldable plastic material selected from the group consisting of polyethylene, polypropylene, polysulfone, polycarbonate, and acrylonitrile-butadience-styrene. The filter elements may take various shapes and could, for example, be cuboid shaped, cylindrically shaped, or shaped in the form of flat or curved rectangular plates.
Further, the filter system may be such that the first manifold includes a cylindrical hub to which the first rodlike end of each of the filter elements can be connected and the second manifold includes a cylindrical hub to which the second rod-shaped end of each of the filter elements can be connected.
In addition the first and second hydraulic means for connecting the first and second manifolds, respectively, to the chamber comprise conduit arms open at both ends.
In another embodiment of the invention, a flow control device is located in the liquid flowpath between the first and the second ends of the plurality of filter elements such that the flow of liquid during the backwash cycle is restricted in the axial direction and is enhanced in the radial direction. In a preferred embodiment, the flow control device is a restriction orifice.
In a preferred embodiment, the present invention takes the form of a filter system for filtering a liquid comprising (a) a tank having a fixed body and a removable cover, said body having an inlet port, a first manifold port and a second manifold connecting port; (b) a removable filter assembly disposed within said tank, said filter assembly comprised of a first manifold, a second manifold, and a plurality of like, curved filter elements, each of said filter elements being comprised of a backbone grid main channel open at a first end and a second end, ribs attached to said backbone grid main channel and extending outwardly therefrom to form a substantially rigid skeletal grid, a woven septum stretched over the entire surface of the skeletal grid, said backbone grid main channel extending substantially through the length of the woven septum with its first and second ends projecting therethrough, and said ribs and the backbone grid main channel connected together in such a way that the filtered liquid flows from the direction of the ribs into the backbone grid main channel and out through one of either the first or the second end of the backbone channel, said first manifold including a central hub having a plurality of element connecting ends extending outwards from the central hub and with means to couple the first end of the backbone grid main channel of each of the filter elements to the first manifold, and a conduit arm in fluid communication with the first manifold port in said body, said second manifold including a central hub having a plurality of element connecting ends extending outwards from the central hub and with means to couple the second end of the backbone grid main channel of each of the filter elements to the second manifold, and a conduit arm in fluid communication with the second manifold port in said body, said filter assembly being disposed in a flow path of the liquid passing into and out of said tank; (c) a pump means in fluid communication with an inlet line for the liquid to be filtered, with said ports in said tank, and with return and waste lines, said pump means being capable of causing said liquid to flow into and out of said ports in said tank, through said filter elements, and the first and second manifolds and out through said return or waste lines and further being capable of causing said liquid to by-pass said tank and flow out of said return or waste lines; and (d) a multifunctional valve means in fluid communication with said pump means, with said ports in said tank, and with said return and waste lines and having: a first control means having open and closed states and capable of controlling the flow of said liquid into said inlet port through said filter elements and said first manifold and said first manifold port, and out through said return line; a second control means having open and closed states and capable of controlling the flow of said liquid into said first manifold port, through said first manifold and filter elements and through said inlet port, and out through said waste line; a third control means having open and closed states and capable of controlling the flow of said liquid into said second manifold port, through said second manifold and filter elements and through said inlet port, and out through said waste line; a fourth control means having open and a closed states and capable of controlling the flow of said liquid by-passing said tank out of said return line; a fifth control means having open and closed states and capable of controlling the flow of said liquid by-passing said tank out of said waste line; and means for moving each of said first, second, third, fourth and fifth control means between their respective open and closed states.
In another form of the above embodiment, the backbone grid main channel may contain a flow control device, which preferably is a restriction orifice. Further, the backbone grid main channel may be in the form of a conduit, or may even be comprised of more than one conduit.
In another preferred embodiment, the present invention takes the form of a filter system for filtering a liquid comprising (a) a tank having a fixed body and a removable cover, said body having an inlet port, a first manifold port and a second manifold connecting port; (b) a removable filter assembly disposed within said tank, said filter assembly comprised of a first manifold, a second manifold, and a plurality of like, curved filter elements, each of said filter elements being comprised of a backbone grid main channel open at a first end and a second end, ribs attached to said backbone grid main channel and extending outwardly therefrom to form a substantially rigid skeletal grid, a woven septum stretched over the entire surface of the skeletal grid, said backbone grid main channel extending substantially through the length of the woven septum with its first and second ends projecting therethrough, and said ribs and the backbone grid main channel connected together in such a way that the filtered liquid flows from the direction of the ribs into the backbone grid main channel and out through one of either the first or the second end of the backbone channel, said first manifold including a central hub having a plurality of element connecting ends extending outwards from the central hub and with means to couple the first end of the backbone grid main channel of each of the filter elements to the first manifold, and a conduit arm in fluid communication with the first manifold port in said body, said second manifold including a central hub having a plurality of element connecting ends extending outwards from the central hub and with means to couple the second end of the backbone grid main channel of each of the filter elements to the second manifold, and a conduit arm in fluid communication with the second manifold port in said body, said filter assembly being disposed in a flow path of the liquid passing into and out of said tank; (d) an inlet conduit for the liquid to be filtered; (e) a filtered liquid return conduit; (f) a backwash waste conduit; (g) a pump means in fluid communication with the inlet conduit for the liquid to be filtered, with said inlet port and manifold ports in said tank, and with the filtered liquid return conduit and the backwash waste conduit, said pump means being capable of causing said liquid to flow into and out of said inlet and manifold ports in said tank, through said filter elements, and the first and second manifolds and out through said filtered liquid return conduit and the backwash waste conduit; and (h) a valve and pipe means in fluid communication with said pump means, with said inlet port and manifold ports in said tank, and having: (i) a two-position slide valve that can be slid into a filter position or a backwash position, a first port of said slide valve being connected to the inlet conduit for the liquid to be filtered, a second port of said slide valve being connected to the filtered liquid return conduit, and a third port of said slide valve being connected to the backwash waste conduit; (ii) a first conduit connecting a fourth port of said slide valve to the inlet port of the tank; (iii) a three-way valve; (iv) a second conduit connecting the first manifold port of the tank to a first port of the three-way valve; (v) a third conduit connecting the second manifold port of the tank to a second port of the three-way valve; and (vi) a fourth conduit connecting a third port of the three way valve to a fifth port of said slide valve.
In another form of the above embodiment, the backbone grid main channel may contain a flow control device, which preferably is a restriction orifice. Further, the backbone grid main channel may be in the form of a conduit, or may even be comprised of more than one conduit.